Estuaries in the southeastern USA have experienced increased loading of contaminants from nonpoint source runoff as well as changes in habitat (e.g., loss of wetlands) due to urbanization. These ...changes may pose significant risks to estuarine fauna, including crustaceans. Several studies have shown relationships between land use classification and levels of stress in estuarine populations. The grass shrimp of the genus
Palaemonetes
is one of the dominant species found in estuarine tidal creeks, accounting for more than 50 % of all macropelagic fauna. Grass shrimp populations were sampled monthly for 3 years at six estuarine creeks on Kiawah Island, SC. Creek watersheds were estimated using National Aerial Photograph Program color infrared and low-altitude true color aerial photography combined with in situ differentially corrected global positioning system mapping of engineered features. Land classifications delineated included water, marsh, buildings, roads, and lawns. Pairwise comparisons for grass shrimp densities among sites showed significant differences on an annual and seasonal basis. Significant relationships (
p
< 0.05) between land class variables and grass shrimp density were identified both annually and seasonally. These findings suggest an influence of land use on
Palaemonetes
spp. populations.
Ambient sediments were collected from a reference site in the North Edisto River, SC and transferred to a laboratory facility to investigate effects of chemical contaminants on estuarine infaunal ...communities under controlled mesocosm conditions. Sediment contaminant slurries were prepared using dried sediments collected from the reference site and spiked with a metal (copper), a polycyclic aromatic hydrocarbon (pyrene), and a pesticide (4,4′-dichlorodiphenyltrichloroethane) to yield nominal mean effects range-median (ERM) quotients of <0.01 (no addition), 0.1, and 1.0 and applied to control, low dose (TRT A), and high dose (TRT B) treatment groups, respectively. Sediment samples for contaminant and benthic analyses were collected at the start of the experiment, 1 month after dosing, and 3 months after dosing. Near-nominal mean ERM quotients of 0.001, 0.075, and 0.818 were measured initially after dosing and remained fairly constant throughout the experiment. Measures of benthic condition, diversity, and richness were significantly reduced in both treatment groups relative to the control 1 month after dosing and persisted in TRT B at 3 months. The results demonstrate that benthic community effects can be observed at mean ERM quotients that are about an order of magnitude lower than levels that have been shown to be associated with significant toxicity in acute laboratory bioassays with single species (e.g., amphipods) in other studies.
Abstract Aims The initial aims were to use recently available observations of glioblastomas (as part of a previous study) that had been imaged twice without intervening treatment before receiving ...radiotherapy in order to obtain quantitative measures of glioma growth and invasion according to a new bio-mathematical model. The results were so interesting as to raise the question whether the degree of radio-sensitivity of each tumour could be estimated by comparing the model-predicted and actual durations of survival and total numbers of glioma cells after radiotherapy. Materials and methods The gadolinium-enhanced T1-weighted and T2-weighted magnetic resonance imaging volumes were segmented and used to calculate the velocity of radial expansion ( v ) and the net rates of proliferation (ρ) and invasion/dispersal ( D ) for each patient according to the bio-mathematical model. Results The ranges of the values of v , D and ρ show that glioblastomas, although clustering at the high end of rates, vary widely one from the other. The effects of X-ray therapy varied from patient to patient. About half survived as predicted without treatment, indicating radio-resistance of these tumours. The other half survived up to about twice as long as predicted without treatment and could have had a corresponding loss of glioma cells, indicating some degree of radio-sensitivity. These results approach the historical estimates that radiotherapy can double survival of the average patient with a glioblastoma. Conclusions These cases are among the first for which values of v , D and ρ have been calculated for glioblastomas. The results constitute a ‘proof of principle’ by combining our bio-mathematical model for glioma growth and invasion with pre-treatment imaging observations to provide a new tool showing that individual glioblastomas may be identified as having been radio-resistant or radio-sensitive.
Toxicity effects of the antifouling compound, Irgarol 1051, were examined using a simulated estuarine salt marsh ecosystem. The 35 day mesocosm exposure incorporated tidal flux and contained ...seawater, sediments, marsh grass, and estuarine biota. Irgarol (10.0 μg/l) caused a significant reduction in phytoplankton biomass and primary productivity. HPLC pigment analysis indicated significant effects of irgarol on both phytoplankton and periphyton community composition, with decreased concentrations of pigments representative of diatom species. There was also a significant decrease in dissolved oxygen levels in the 10.0 μg/l irgarol treatment. Growth of the hard shell clam was significantly reduced in the 1.0 and 10.0 μg/l irgarol treatments. The effects observed occurred at irgarol concentrations greater than those typically measured in the environment. Prolonged exposure, the accumulation of irgarol in sediments, plant, or animal tissues, and the interaction of irgarol with other chemicals in the environment; however, could increase risk.
Rice irrigation-water use was estimated in Mississippi (MS) and Arkansas (AR) in 2003 and 2004. Irrigation inputs were compared on naturally sloping (i.e. contour-levee system) and mechanically ...graded fields. In MS, rice production consumed, on average, 895 mm water, but irrigation inputs were greatly affected by production system. Contour-levee systems accounted for 35% of the production area and consumed 1,034 mm irrigation. Fields mechanically graded to a consistent slope of approximately 0.1% (i.e. straight-levee systems) consumed 856 mm irrigation and accounted for 60% of the production area. Fields devoid of slope (i.e. zero-grade system) accounted for 5% of the production area and consumed 382 mm irrigation. In AR, contour-levee rice production consumed 789 mm compared to 653 mm with a straight-levee system. Using low pressure, thin wall (9-10 mil) disposable irrigation tubing to deliver water to each paddy independently reduced irrigation inputs by 28% in MS and 11% in AR when compared to a single-point (levee-gate) distribution system.
Phytoplankton are potentially more at risk to the adverse effects of herbicides than many other organisms in estuarine ecosystems. The focus of this study was to characterize the toxicity of a widely ...used herbicide, atrazine, to a single species of phytoplankton. The nanoplankter Pavlova sp. was grown under controlled laboratory conditions and was used to elucidate short‐term, high‐level population effects of atrazine. Secondly, a long‐term, multigenerational population exposure was performed with a low level of atrazine followed by an additional short‐term, high‐level exposure on the same population with no recovery period. The 96–h growth rate of 50% effective concentration (EC50) for Pavlova sp. was 147 μg/L (95% CI = 116.4–178.7 μg/L). Long‐term exposure at 20 μg/L for four (batch culture) growth cycles (∼20 generations) had no significant effect on the growth rate of Pavlova sp. except during the fourth growth cycle. However, a subsequent short‐term, high‐level 96–h exposure inoculated from the long‐term, low‐level exposed population showed increased sensitivity to atrazine (96–h growth rate EC50 = 96.0 μg/L, 95% CI = 90.2–103.7 μg/L). Multigenerational exposure to atrazine appeared to render phytoplankton significantly more sensitive (35%) to atrazine effects. Given the documented persistence of atrazine in surface waters, long‐term exposure to low levels of atrazine without recovery may lead to shifts in species sensitivity and potential alterations in phytoplankton population dynamics.
Atrazine effects on the microbial food web were assessed in mesocosms designed to simulate a southeastern tidal creek ecosystem. The test chambers simulate the major features unique to estuarine ...systems, such as tidal flow and salinity changes. Microbial communities were colonized on artificial substrates and analyzed for productivity, biomass, and community composition. Atrazine was found to reduce chlorophyll
a, phototrophic carbon assimilation and phototrophic biovolume in the 40 and 160 μg l
−1 treatments. Significant reductions in phototrophic variables occurred within 24 h of pesticide exposure and no recovery was detected after 9 days. Dissolved oxygen content in the mesocosms was not significantly affected by atrazine. Atrazine induced changes in composition of the algal community. Most taxa were reduced in abundance by atrazine exposure; however, cyanobacterial taxa generally became more abundant. Bacterial abundance was significantly elevated in the highest dose after 24 h, but decreased in a dose–response manner after 48 h. There was no significant effect on small ciliates; however, large ciliates and small flagellates increased significantly in number after 48 h and remained elevated after 9 days. Atrazine at 160 μg l
−1 significantly reduced large flagellate density throughout the experiment. These results suggest that exposure of the estuarine microbial food web to agricultural pesticides can lead to both functional and structural changes, which may potentially impact higher trophic levels.
The mechanisms underlying age-related loss of muscle and bone tissue are poorly understood but are thought to involve changes in sex hormone status, physical activity, and circulating levels of ...inflammatory cytokines. This study attempts to develop an animal model useful for evaluating these mechanisms in vivo. Male C57BL/6 mice were included for study at 3, 6, 12, 18, 24, and 29 months of age. Endocortical mineralizing surface, serum leptin, body weight, and percentage of body fat all increased between 6 and 12 months of age as activity level declined. Serum levels of the inflammatory marker IL-6 increased significantly after 12 months of age, following the observed increase in body weight and percent body fat. Hindlimb muscle mass declined significantly between 18 and 24 months of age, both absolutely and relative to total body mass, with a further decline (∼15%) between 24 and 29 months. Loss of muscle mass after 18 months of age was accompanied by a significant increase in bone resorption, as indicated by serum pyridinoline cross-links, and a significant decrease in fat mass, serum leptin, bone strength, bone mineral density, and vertical cage activity. No significant changes in serum testosterone with aging were detected in the mice, as levels were essentially constant between 6 and 29 months. Our data show that mice lose a significant amount of muscle and bone tissue with age, and this loss of musculoskeletal tissue is accompanied by a drop in serum leptin and preceded by a significant decrease in physical activity.
Legume systematists have been making great progress in understanding evolutionary relationships within the Leguminosae (Fabaceae), the third largest family of flowering plants. As the phylogenetic ...picture has become clearer, so too has the need for a revised classification of the family. The organization of the family into three subfamilies and 42 tribes is outdated and evolutionarily misleading. The three traditionally recognized subfamilies, Caesalpinioideae, Mimosoideae, and Papilionoideae, do not adequately represent relationships within the family. The occasion of the Sixth International Legume Conference in Johannesburg, South Africa in January 2013, with its theme “Towards a new classification system for legumes,” provided the impetus to move forward with developing a new classification. A draft classification, based on current phylogenetic results and a set of principles and guidelines, was prepared in advance of the conference as the basis for discussion. The principles, guidelines, and draft classification were presented and debated at the conference. The objectives of the discussion were to develop consensus on the principles that should guide the development of the classification, to discuss the draft classification's strengths and weaknesses and make proposals for its revision, and identify and prioritize phylogenetic deficiencies that must be resolved before the classification could be published. This paper describes the collaborative process by a large group of legume systematists, publishing under the name Legume Phylogeny Working Group, to develop a new phylogenetic classification system for the Leguminosae. The goals of this paper are to inform the broader legume community, and others, of the need for a revised classification, and spell out clearly what the alternatives and challenges are for a new classification system for the family.
•The Leguminosae is in need of an updated classification.•Legume Phylogeny Working Group has initiated a project to revise the classification.•The project was initiated for the International Legume Conference in Johannesburg.•We describe the challenges and decisions faced in revising the classification.
PDF
